Hello Dale,
I have worked on many one-piece units already, mostly commercial. Most
started as roof-top units.
The idea was applied to homes and trailer homes. They come complete,
ready to run. Hook up duct for supply and return, usually done with a matching
kit for the unit you got. You supply the power line and thermostat wires to it
and you are running.
The units usually last at least 20 years without hardly any trouble if,
the power line is heavy to handle the starting current with ease, and the
condenser coil is hosed off every year.
Most of the time the unit just sits near ground level which is the reason
they need a cleaning so often with mower clipping and crap.
A lot of times there is one main cover for getting to things. It will
allow you do get to the condenser motor, evaporator coil and motor. With the
cover in place it seals both compartments and keeps them separate.
The reason they last so long is no idiot has to hook anything together or
rig something to work, just power, duct connection and control thermostat. The
cost is cheaper since most labor is in a factory.
They come in any form factor, heat and A/C, gas , oil, electric heat, heat
pump with gas back-up. You want it, you can get it. A nice one was made in
Canada with dual compressors which was efficient down to zero degrees F.
............bob
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